An early morning pipe-bomb explosion blew out the windows of an unoccupied van parked outside a theater owned by a former star of TV's "The Sopranos," police said Tuesday.

The New York Police Department said it did not know whether the incident had any connection to the actor, Michael Imperioli, who owns Studio Dante. Imperioli played Christopher Moltisanti, Tony Soprano's nephew, on the popular HBO television show.

His representative did not immediately return calls for comment on Tuesday.

NYPD spokesman Paul Browne said there had been "no known threats to the location or its owners" before the 1 a.m. incident. Investigators believe someone planted the device — a fused pipe bomb — on a tiled ledge near the theater entrance before it exploded, he said.

The blast damaged the van parked in front of the building but "thankfully no one was injured," said Mayor Michael Bloomberg.

Three residential floors above the theater were evacuated while the bomb squad made sure they were safe after the 1 a.m. incident. The owner of the van, who lives nearby, was unharmed, police said.

"While there certainly is no evidence that this was terrorism, we are taking this and every act of violence extremely seriously, and we'll take every step to identify and apprehend whoever set this explosive device off," said Bloomberg.

Studio Dante is described on its Web site as "an unexpected jewel-box that was built to house progressive new plays." Imperioli created it with his wife, Victoria.

Though police sometimes recover pipe bombs while making arrests, explosions are rare. One exception came in 2004, when an emotionally disturbed police officer set off a pipe bomb inside a Times Squares subway station; he was sentenced to one to three years in prison for reckless endangerment.

In 2005, an explosion caused by two makeshift grenades fitted with fuses blew out a window near Manhattan's British consulate. There were no injuries or arrests.